I have a site running v10.8.6 running with ModelsMode set to InMemory. I noticed that the front end of the site will crash when I add a new Prevalue to an existing Data Type. The logs show an InvalidCastException that indicates the cached content models are corrupt. The front end can be recovered by rebuilding the content cache under Settings. Is there a relationship between saving the Data Type and the content cache? If there is, I think my expectation would be the cache is rebuilt similarly to when a content page is saved.